This invention relates to implantable medical devices, such as implantable medical devices that include a surface layer that promotes vascularization.
A limitation of implanted medical devices is the rejection of the material by a process known as the foreign body response. Initially, inflammatory cells, especially macrophages, perceive the surface of most implanted materials as foreign, or as non-natural. These cells initiate a cascade of cellular and tissue reactions leading to a physiological state of chronic inflammation and fibrous encapsulation of the implanted device. In its mature form, the fibrous capsule prevents both humoral and cellular communication with the surrounding tissue.
One way to mitigate this problem is to promote the vascularization of the tissue surrounding the implanted device. In one aspect, the present invention provides biocompatible materials that can be applied to implantable medical devices to promote surface vascularization of the implanted device, thereby reducing or eliminating the foreign body reaction. The present invention also provides methods of making the biocompatible materials.
In one aspect, the present invention provides implantable medical devices comprising: (a) a device body; and (b) a surface layer attached to at least a portion of the device body, the surface layer comprising: a surface layer body that defines an internal surface, attached to the device body, and an external surface; and a multiplicity of blood vessels disposed within the surface layer body, the blood vessels opening onto the external surface of the surface layer body. Typically, the surface layer is attached to the device body at the location(s) on the device body which are known to stimulate a foreign body reaction, or are likely to stimulate a foreign body reaction.
In another aspect, the present invention provides methods of making implantable medical devices. The methods of this aspect of the invention comprise the steps of: (a) contacting an angiogenic biological material with a biocompatible material under conditions that enable the growth of blood vessels from the angiogenic biological material into the biocompatible material; (b) separating the biocompatible material from the angiogenic biological material under conditions that retain within the biocompatible material at least a portion of the blood vessels that have grown into the biocompatible material; and (c) incorporating the biocompatible material prepared in accordance with steps (a) and (b) into an implantable medical device.
In another aspect, the present invention provides synthetic biocompatible materials comprising: (a) a substrate defining at least one surface, provided that the substrate is not collagen; and (b) a multiplicity of blood vessels disposed within the substrate, the blood vessels opening onto at least one surface of the at least one substrate surface.
The synthetic biocompatible materials of the invention are useful, for example, for making the surface layer of the implantable medical devices of the invention. The implantable medical devices of the invention are useful, for example, in any situation where it is desired to reduce the foreign body reaction to an implanted medical device.